This invention relates to an apparatus for controlling quantity of the exhaust-gas and the air supplied into the intake system, (hereinafter referred to as "intake regulator"), of the internal combustion engine depending on its operating conditions.
Generally, exhaust-gas recirculation systems for the internal combustion engine are provided to decrease noxious nitrogen oxides in the engine exhaust-gas. They reduce the nitrogen oxides emissions by lowering the combustion temperature by recirculating part of the exhaust-gas through the engine intake system into the cylinders.
But, the recirculation of the exhaust-gas is usually accompanied by a decrease in fuel combustion efficiency in the cylinders. Excessive exhaust-gas recirculation sharply lowers power output and mileage, impairs driveability, and causes engine stop and other troubles.
Therefore, the quantity of recirculated exhaust-gas has been controlled by complex procedures according to varying engine operating conditions, with consideration for nitrogen oxides emissions, power output and mileage.
In addition to the aforesaid exhaust-gas recirculation system, the lean mixture combustion system has been known as a measure of reducing the production of nitrogen oxides in the combustion process. This system comprises achieving good combustion of an air-fuel mixture whose air-fuel ratio is considerably larger than stoichiometric, as between 16 and 23, for instance. Since such lean air-fuel mixtures, in general, are low in ignitability and combustibility, various corrective measures have been employed.
For example, auxiliary combustion chamber, stratified-charge and turbulence methods are known. These methods improve ingnitability by leading a layer of rich mixture of air and fuel to or scavenging the vicinity of the spark plug and enhance combustibility by increasing the flame propagation speed by producing strong turbulent flow.
The above-mentiond two nitrogen oxides reducing systems have both merits and demerits. The exhaust-gas recirculation system achieves high nitrogen oxides reduction, but impairs power output and mileage, as mentioned before. In contrast, the lean mixture combustion system involves difficult air-fuel ratio control in the carburetor and low nitrogen oxides reduction, but improves mileage and provides better driveability as compared with the exhaust-gas recirculation system.